Bespoke markdown?

I’d like to introduce an additional tag, or markdown like the link tags, in the descriptions. Could someone point me in the right direction in the code to have a look at please. Having worked with python and django, this source code baffles me most of the time - my problem i know.

Would want to interpret and translate something like “mycontent” in any text to a bit of html to display an image. The image would be served by an external REST server that is fed the mycontent bit through an http://… call, and returns an image.

Would that have to happen in main kanboard code, or can I do it as a plugin?

Thank you
Will

PS would like to add some chemical awareness in the form of smiles structure depiction. Smiles strings code for molecules.